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    Subject[patch 17/28] fs: increase d_name lock coverage
    Cover d_name with d_lock in more cases, where there may be concurrent
    modification to it.

    Signed-off-by: Nick Piggin <npiggin@kernel.dk>

    ---
    fs/dcache.c | 23 ++++++++++++++++-------
    1 file changed, 16 insertions(+), 7 deletions(-)

    Index: linux-2.6/fs/dcache.c
    ===================================================================
    --- linux-2.6.orig/fs/dcache.c 2010-11-17 00:52:37.000000000 +1100
    +++ linux-2.6/fs/dcache.c 2010-11-17 01:05:42.000000000 +1100
    @@ -1361,16 +1361,20 @@ static struct dentry *__d_instantiate_un
    list_for_each_entry(alias, &inode->i_dentry, d_alias) {
    struct qstr *qstr = &alias->d_name;

    + spin_lock(&alias->d_lock);
    if (qstr->hash != hash)
    - continue;
    + goto next;
    if (alias->d_parent != entry->d_parent)
    - continue;
    + goto next;
    if (qstr->len != len)
    - continue;
    + goto next;
    if (memcmp(qstr->name, name, len))
    - continue;
    - dget_locked(alias);
    + goto next;
    + dget_locked_dlock(alias);
    + spin_unlock(&alias->d_lock);
    return alias;
    +next:
    + spin_unlock(&alias->d_lock);
    }

    __d_instantiate(entry, inode);
    @@ -2298,7 +2302,9 @@ static int prepend_path(const struct pat
    }
    parent = dentry->d_parent;
    prefetch(parent);
    + spin_lock(&dentry->d_lock);
    error = prepend_name(buffer, buflen, &dentry->d_name);
    + spin_unlock(&dentry->d_lock);
    if (!error)
    error = prepend(buffer, buflen, "/", 1);
    if (error)
    @@ -2506,10 +2512,13 @@ static char *__dentry_path(struct dentry

    while (!IS_ROOT(dentry)) {
    struct dentry *parent = dentry->d_parent;
    + int error;

    prefetch(parent);
    - if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
    - (prepend(&end, &buflen, "/", 1) != 0))
    + spin_lock(&dentry->d_lock);
    + error = prepend_name(&end, &buflen, &dentry->d_name);
    + spin_unlock(&dentry->d_lock);
    + if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
    goto Elong;

    retval = end;



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